Switchable structured bond: A bond graph device for modeling power coupling/decoupling of physical systems

摘要

This paper presents a controlled Bond Graph interconnection structure named Switchable Structured Bond, or SS-Bond for short, basically intended for modeling and simulation of ideal switching phenomena (zero transition time) with fixed causality. Serving to model the presence or absence of a power preserving connection between two power ports, these new structures are inspired in the idea yielding the switch-able bond (or SB) formalism, but embody some features correcting the shortcomings of the latter. Indeed, when both power ports are connected, both the SB and the SS-Bond behave like a standard power bond, but when the power connection is absent, the SS-Bond fully captures the possible states of the adjacent power ports, unlike the SB, which in many cases leaves undefined the situation of these ports. As SS-Bonds are originally defined to model ideal switching, these possible states are zero-flow or zero-effort for each of the disconnected power ports. These four situations, together with the normally connected state, define the five possible switching modes of an SS-Bond. The SS-Bonds can be internally represented with standard bond graph elements. To keep fixed the causality assignment even under switching, some algebraic constraints are added to the equation set of the switched structure, which in the Bond Graph domain can be represented with residual sinks. A minor modification on the internal implementation of the SS-Bonds allows the formalism for commutation modeling with the non-ideal approach consisting in adding parasitic components to avoid causality changes. Besides some models of electric-electronic circuits, slip-stick friction in a simple mechanical system and abrupt faults in a hydraulic two tank system are used to illustrate the new formalism and its performance in modeling and simulation.